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PANGAEA - Publishing Network for Geoscientific & Environmental Data (728,460 recursos)
The information system PANGAEA is operated as an Open Access library aimed at archiving, publishing and distributing georeferenced data from earth system research. The system guarantees long-term availability of its content through a commitment of the operating institutions.

Datasets with PANGAEA technical keyword @IMAGES

Mostrando recursos 1 - 20 de 1,435

1. Paleoenvironmental analysis of sediment core MD03-2601 - Denis, Delphine; Crosta, Xavier; Schmidt, Sabine; Carson, Damien S; Ganeshram, Raja S; Renssen, Hans; Bout-Roumazeilles, V; Zaragosi, Sebastien; Martin, Bernard; Cremer, Michel; Giraudeau, Jaques
This study presents a high-resolution multi-proxy investigation of sediment core MD03-2601 and documents major glacier oscillations and deep water activity during the Holocene in the Adélie Land region, East Antarctica. A comparison with surface ocean conditions reveals synchronous changes of glaciers, sea ice and deep water formation at Milankovitch and sub-Milankovitch time scales. We report (1) a deglaciation of the Adélie Land continental shelf from 11 to 8.5 cal ka BP, which occurred in two phases of effective glacier grounding-line retreat at 10.6 and 9 cal ka BP, associated with active deep water formation; (2) a rapid glacier and sea...

2. CaCO3 content, terrigenous components, foraminifera abundance and age of sediment core MD95-2006, Barra Fan, UK - Knutz, Paul Cornils; Austin, William EN; Jones, EJW
Lithology, lithic petrology, planktonic foraminiferal abundances, and clastic grain sizes have been determined in a 30 m-long core recovered from the Barra Fan off northwest Scotland. The record extends back to around 45 kyr B.P., with sedimentation rates ranging between 50 and 200 cm/kyr. The abundance of ice-rafted debris indicates 16 glacimarine events, including temporal equivalents to Heinrich events 1-4. Enhanced concentrations of basaltic material derived from the British Tertiary Province suggest that the glacimarine sediments record variations in a glacial source on the Hebrides shelf margin. Glacimarine zones are separated by silty intervals with high planktonic foraminifera concentrations that...

3. CaCO3 content, terrigenous components, foraminifera abundance and age of sediment core MD95-2006, Barra Fan, UK - Knutz, Paul Cornils; Austin, William EN; Jones, EJW
Lithology, lithic petrology, planktonic foraminiferal abundances, and clastic grain sizes have been determined in a 30 m-long core recovered from the Barra Fan off northwest Scotland. The record extends back to around 45 kyr B.P., with sedimentation rates ranging between 50 and 200 cm/kyr. The abundance of ice-rafted debris indicates 16 glacimarine events, including temporal equivalents to Heinrich events 1-4. Enhanced concentrations of basaltic material derived from the British Tertiary Province suggest that the glacimarine sediments record variations in a glacial source on the Hebrides shelf margin. Glacimarine zones are separated by silty intervals with high planktonic foraminifera concentrations that...

4. Magnesium/Calcium ratios and sea surface temperature estimation for sediments of the Timor Sea - Xu, Jian; Kuhnt, Wolfgang; Holbourn, Ann EL; Andersen, Nils; Bartoli, Gretta
We use a multiproxy approach to monitor changes in the vertical profile of the Indonesian Throughflow as well as monsoonal wind and precipitation patterns in the Timor Sea on glacial-interglacial, precessional, and suborbital timescales. We focus on an interval of extreme climate change and sea level variation: marine isotope (MIS) 6 to MIS 5e. Paleoproductivity fluctuations in the Timor Sea follow a precessional beat related to the intensity of the Australian (NW) monsoon. Paired Mg/Ca and d18O measurements of surface- and thermocline-dwelling planktonic foraminifers (G. ruber and P. obliquiloculata) indicate an increase of >4°C in both surface and thermocline water...

5. Planktonic foraminiferal and stable oxygen isotope record of Holocene sediments from the Norwegian Sea - Risebrobakken, Bjoerg; Jansen, Eystein; Andersson, Carin; Mjelde, Eirik; Hevroy, Kjersti
High-resolution records from IMAGES core MD95-2011 in the eastern Norwegian Sea provide evidence for relatively large- and small-scale high-latitude climate variability throughout the Holocene. During the early and mid-Holocene a situation possibly driven by consistent stronger westerlies increased the eastward influence of Arctic intermediate and near-surface waters. For the late Holocene a relaxation of the atmospheric forcing resulted in increased influence of Atlantic water. The main changes in Holocene climate show no obvious connection to changing solar irradiance, and spectral analysis reveals no consistent signature for any periodic behavior of Holocene climate at millennial or centennial timescales. There are, however,...

6. Carbon and alkenone analysis on sediment core MD97-2151 - Zhao, Meixun; Huang, Chi-Yue; Wang, Chia-Chun; Wei, Ganjian
We report 150 kyr records of U37K' sea-surface temperature (SST) and carbonate content with 150-200-year sampling resolution from the southern South China Sea (SCS) in the northern margin of the Western Pacific Warm Pool (WPWP) using IMAGES Core MD972151. The glacial/interglacial SST change is about 5 °C for Termination II (23.5 to 28.5°C) and 4°C for Termination I (24 to 28°C). The simultaneous rise of sea level and U37K' SST during Termination I suggests that sea-level change has played an important role in the SCS SST variability by influencing the exchange of tropical ocean warm surface water with the SCS...

7. Sedimentology of the Okhotsk Sea - Nürnberg, Dirk; Tiedemann, Ralf
On the basis of two sedimentary records from the central Sea of Okhotsk, we reconstruct the closely coupled glacial/interglacial changes in terrigenous flux, marine productivity, and sea ice coverage over the past 1.1 Myr. The correspondance of our sedimentary records to the China loess grain size record (China loess particle timescale, CHILOPARTS) suggests that environmental changes in both the Sea of Okhotsk area and in SE Asia were closely related via the Siberian atmospheric high-pressure cell. During full glacial times our records point to a strong Siberian High causing northerly wind directions, the extension of the sea ice cover, and...

8. Sedimentology of the Okhotsk Sea - Nürnberg, Dirk; Tiedemann, Ralf
On the basis of two sedimentary records from the central Sea of Okhotsk, we reconstruct the closely coupled glacial/interglacial changes in terrigenous flux, marine productivity, and sea ice coverage over the past 1.1 Myr. The correspondance of our sedimentary records to the China loess grain size record (China loess particle timescale, CHILOPARTS) suggests that environmental changes in both the Sea of Okhotsk area and in SE Asia were closely related via the Siberian atmospheric high-pressure cell. During full glacial times our records point to a strong Siberian High causing northerly wind directions, the extension of the sea ice cover, and...

9. Sea surface reconstruction of sediment cores off West Spitsbergen - Hald, Morten; Ebbesen, Hanne; Forwick, Matthias; Godtliebsen, Fred; Khomenko, Liza; Korsun, Sergei; Ringstad Olsen, Lena; Vorren, Tore O
Two sediment cores from the West Spitsbergen area, Euro-Arctic margin, MD99-2304 and MD99-2305, have been investigated for paleoceanographic proxies, including benthic and planktonic foraminifera, benthic foraminiferal stable isotopes and ice rafted debris. Core MD99-2304 is located on the upper continental margin, reflecting variations in the influx of Atlantic Water in the West Spitsbergen Current. Core MD99-2305 is located in Van Mijenfjord, picturing variations in tidewater glacier activity as well as fjord-ocean circulation changes. Surface water warmer than today, was present on the margin as soon as the Van Mijenfjord was deglaciated by 11,200 cal. years BP. Relatively warm water invaded...

10. Age determination of sediment cores of the Golf of Lions - Beaudouin, Célia; Dennielou, Bernard; Melki, Tarek; Guichard, Francois; Kallel, Nejib; Berné, Serge; Huchon, Agnes
Siliciclastic turbidites represent huge volumes of sediments, which are of particular significance for (1) petroleum researchers, interested in their potential as oil reservoirs and (2) sedimentologists, who aim at understanding sediment transport processes from continent to deep-basins. An important challenge when studying marine turbidites has been to establish a reliable chronology for the deposits. Indeed, conventional marine proxies applied to hemipelagic sediments are often unreliable in detrital clays. In siliciclastic turbidites, those proxies can be used only in hemipelagic intervals, providing a poor constraint on their chronology. In this study, we have used sediments from the Rhône Neofan (NW Mediterranean...

11. Stable oxygen isotope record and terrigenous components of sediment core MD96-2094 - Stuut, Jan-Berend; Prins, Maarten A; Schneider, Ralph R; Weltje, Gert Jan; Jansen, J H Fred; Postma, George
The terrigenous fraction of sediments recovered from Walvis Ridge, SE Atlantic Ocean, reveals a history of southwestern African climate of the last 300 kyr. End-member modelling of a data set of grain-size distributions (n=428) results in three end members. The two coarsest end members are interpreted as eolian dust, the third end member as hemipelagic mud. The ratio of the two eolian end members reflects the eolian grain size and is attributed to the intensity of the SE trade winds. Trade winds were intensified during glacials compared to interglacials. Changes in the ratio of the two eolian end members over...

12. Paleomagnetic and beryllium isotope record of West Equatorial Pacific sediments - Carcaillet, Julien; Thouveny, Nicolas; Bourles, Didier L
The reliability of paleomagnetic records as proxies of the geomagnetic field intensity is still a matter of controversy since volcanic materials hardly provide continuous records, and marine sediments are suspected to carry a remanence biased by post-depositional realignments and/or by overprints. Such long standing debate emphasizes the need for the development of methods independent from paleomagnetism to decipher geomagnetic intensity variations. High resolution measurements of authigenic 10Be/9Be along with a detailed sedimentary record of directional and relative paleointensity variations evidence, over the 0.6-1.3 Ma time interval, frequent and recurrent excursions or short events in the late Matuyama and the early...

13. Beryllium isotopes of sediments from the Portuguese margin - Carcaillet, Julien; Bourles, Didier L; Thouveny, Nicolas; Arnold, Maurice
A high resolution study of authigenic Be isotopes (10Be and 9Be) combined with continuous relative paleointensity records has been performed along the same marine sedimentary sequences from the Portuguese margin (NE Atlantic) covering the past 300 kyr in order to assess relationships between geomagnetic moment variations and 10Be production rate variations. A careful examination of the various ways of taking into account environmental disturbing effects on the authigenic 10Be concentration leads to the conclusion that the most reliable proxy of cosmonuclide production rates is presently the authigenic 10Be/9Be ratio. Eight intervals of significant authigenic 10Be/9Be enhancement evidence geomagnetic moment drops...

14. Beryllium isotopes of sediments from the Portuguese margin - Carcaillet, Julien; Bourles, Didier L; Thouveny, Nicolas; Arnold, Maurice
A high resolution study of authigenic Be isotopes (10Be and 9Be) combined with continuous relative paleointensity records has been performed along the same marine sedimentary sequences from the Portuguese margin (NE Atlantic) covering the past 300 kyr in order to assess relationships between geomagnetic moment variations and 10Be production rate variations. A careful examination of the various ways of taking into account environmental disturbing effects on the authigenic 10Be concentration leads to the conclusion that the most reliable proxy of cosmonuclide production rates is presently the authigenic 10Be/9Be ratio. Eight intervals of significant authigenic 10Be/9Be enhancement evidence geomagnetic moment drops...

15. Oxygen isotope and Mg/Ca record of planktonic foraminifera of sediment core MD01-2390 - Steinke, Stephan; Chiu, Han-Yi; Yu, Pai-Sen; Shen, Chuan Chou; Erlenkeuser, Helmut; Löwemark, Ludvig; Chen, Min-Te
Changes in the local freshwater budget over the last 22,000 years have been estimated from a sediment core located in the southern South China Sea (SCS) using a combined approach of Mg/Ca and oxygen isotopes on the planktonic foraminifera Globigerinoides ruber (white) sensu stricto (s.s.). Core MD01-2390 (06°28,12N, 113°24,56E; water depth 1591 m) is located near the glacial paleo-river mouths of the Baram, Rajang and North Sunda/Molengraaff Rivers that drained the exposed Sunda Shelf. The delta18Oseawater record reveals lower average values (-0.96±0.18 per mil) during the Last Glacial Maximum (LGM) when compared with modern values (-0.54±0.18 per mil). Low salinity...

16. Stable isotope and Mg/Ca record of Globigerinoides ruger morphotypes - Steinke, Stephan; Chiu, Han-Yi; Yu, Pai-Sen; Shen, Chuan Chou; Löwemark, Ludvig; Mii, Horng-Sheng; Chen, Min-Te
Tests of the planktonic foraminifer Globigerinoides ruber (white; d'Orbigny) have become a standard tool for reconstructing past oceanic environments. Paleoceanographers often utilize the Mg/Ca ratios of the foraminiferal tests for reconstructing low-latitude ocean glacial-interglacial changes in sea surface temperatures (SST). We report herein a comparison of Mg/Ca measurements on sample pairs (n = 20) of two G. ruber (white) morphotypes (G. ruber sensu stricto (s.s.) and G. ruber sensu lato (s.l.)) from surface and downcore samples of the western Pacific and Indian Oceans. G. ruber s.s. refers to specimens with spherical chambers sitting symmetrically over previous sutures with a wide,...

17. Palynology of sediment core MD01-2378 - Kawamura, Hiroshi; Holbourn, Ann EL; Kuhnt, Wolfgang
Climatic conditions in the western Timor Sea and the adjacent northwestern part of Australia are reconstructed for the last 460 ka, based on geochemical and palynological proxy records of paleoproductivity and land vegetation (precipitation) from IMAGES Core MD01-2378. Reduced precipitation and elevated productivity characterize glacial stages, whereas enhanced precipitation and reduced productivity are typical of interglacial stages. A long-term reduction in precipitation over the last 320 ka occurred in two steps at approximately 300 ka and 180 ka BP that are clearly recognizable in the pollen record. Variations in paleoproductivity and paleoclimate in the Timor Sea and adjacent landmasses appear...

18. Stable isotope record and benthic foraminifera of sediment core MD01-2378 - Holbourn, Ann EL; Kuhnt, Wolfgang; Kawamura, Hiroshi; Jian, Zhimin; Grootes, Pieter Meiert; Erlenkeuser, Helmut; Xu, Jian
A high-resolution (~1-2 kyr) multiproxy record from the Timor Sea in the easternmost Indian Ocean (International Marine Global Change (IMAGES) Program Core MD01-2378, latitude 13°04.95'S, longitude 121°47.27'E, 1783 m water depth) closely tracks changes in intermediate water ventilation and paleoproductivity over the last 460 kyr within one of the main outflow passages of the Indonesian Throughflow. Spectral analysis of five different flux-based productivity proxies indicates spectral power concentrated in the 100 kyr (glacial-interglacial) and the 23 kyr and 19 kyr (precessional) periods. Paleoproductivity maxima lead ice volume (benthic delta18O) maxima by 20° to 40° (~1300 to 2600 years) at the...

19. Deep-water temperature reconstruction of sediment core MD99-2334 - Skinner, Luke C; Shackleton, Nicholas J; Elderfield, Henry
Paired measurements of Mg/Ca and delta18O(cc) (calcite delta18O) in benthic foraminifera from a deep-sea core recovered on the Iberian Margin (MD99-2334K; 37°48'N, 10°10'W; 3,146 m) have been performed in parallel with planktonic delta18O(cc) analyses and counts of ice-rafted debris (IRD). The synchrony of temperature changes recorded in the Greenland ice cores and in North Atlantic planktonic delta18O(cc) allows the proxy records from MD99-2334K to be placed confidently on the GISP2 time-scale. This correlation is further corroborated by AMS 14C-dates. Benthic Mg/Ca measurements in MD99-2334K permit the reconstruction of past deep-water temperature (T(dw)) changes since ~34 cal. ka BP (calendar kiloyears...

20. Age determination and stable carbon oxygen isotopes of sediment core MD99-2334 - Skinner, Luke C; Shackleton, Nicholas J
A sequence of accelerator mass spectrometry (AMS) 14C dates performed on benthic and planktonic foraminifera from a northeast Atlantic deep-sea core (MD99-2334K; 37°48'N, 10°10'W; 3146 m) permit the reconstruction of deep water "14C ventilation ages" across the last deglaciation. The records from MD99-2334K have been placed on the GISP2 timescale via the synchrony of temperature changes recorded in the Greenland ice cores and in North Atlantic planktonic delta18O(cc) (calcite delta18O). On the basis of a range of estimates for past source water Delta14C, this permits the estimation of 14C projection ventilation ages for comparison with benthic-planktonic 14C age differences. Although...

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